1. Field of the Invention
This invention relates generally to prosthetic devices and, more particularly, to a prosthetic knee and lower leg assembly which enables an individual, who has had a leg amputation between the hip and knee joints, to participate in demanding athletic activities, such as telemark skiing, alpine skiing, cross-country skiing, water skiing, snow boarding, wake boarding, surfing, skate boarding, wind surfing, rock climbing, ice climbing, roller blading and ice skating, in which the quadriceps are ordinarily used extensively for support and dynamic function.
2. History of the Prior Art
A prosthetic device incorporating a joint for articulation of the knee is an essential element of an artificial leg prosthesis called an “above the knee”, that is to say which has a foot, an ankle, a lower leg portion (hereinafter called a “leg”), a knee and a socket for receiving the stump of the thigh.
Relative movement of the upper part of the prosthetic device (supporting the socket) with respect to the leg may be controlled using one or a combination of the many known prior art techniques.
The basic function that an above the knee must perform is that of hingeable movement at the knee joint. Damping of the movement is typically provided as the patient steps forward on the prosthesis. As the leg moves behind the patient, energy stored during the damping step is released for propulsion. Damping and propulsion is generally provided through the use of springs, hydraulic or pneumatic cylinders, or by some combination of these devices.
The patient can perform a balancing movement with this type of prosthesis. If this movement is controlled in an appropriate manner, the ability to walk in a relatively natural way can thus be restored.
U.S. Pat. No. 6,852,131 to Chen, et al. discloses an artificial knee joint that includes a joint seat, a support frame, a hydraulic device, a push rod, and a biasing member. The joint seat has a joint body and a rotatable member connected pivotally to the joint body and connected fixedly to a residual thigh. The support frame is connected rotatably to the joint body, and is connectedly fixed to a prosthetic lower leg. The push rod is movable relative to the joint body between an extended position, where a free end of the rotatable member is spaced apart from the joint body to align the lower leg with the thigh, and a retracted position, where the free end of the rotatable member abuts against the joint body. The biasing member biases the push rod to the extended position.
U.S. Pat. No. 5,904,721 to Henry, et al. discloses a prosthetic device having a pneumatic device for knee articulation formed of an upper part adapted to support a socket element for a stump of a thigh, and a lower part intended to receive a tube extended by an ankle and foot. The two parts are connected to each other by an assembly of pivoted links forming a deformable prism. Movement of the two parts between two stable positions of complete extension and flexure, about the variable axis of rotation defined by these connections, is controlled by a pneumatic cylinder having an upper chamber and a lower chamber separated by a piston and communicating with each other by an air duct with adjustable flow.
Many sports, such as telemark skiing, alpine skiing, cross-country skiing, water skiing, snow boarding, wake boarding, surfing, wind surfing, rock climbing, ice climbing, roller blading and ice skating require that the participant maintain flexure of the knee joints for extended periods in order to absorb shocks and provide propulsion. The muscles known as the quadriceps enable participants to maintain a bent knee position so that the legs can act as shock absorbers and provide propulsion, as needed. One of the problems associated with conventional above-the-knee prosthetic devices is that, in order to simulate a normal walking or running gait, they are not designed to provide vertical support for the wearer in a bent knee position. Instead of providing support, they collapse to a configuration of complete flexure and must be manually returned to the extended position.